"In a paper published in Global Change Biology, Colleen Iversen, ORNL ecosystem ecologist, and her colleagues quantified the effects of elevated carbon dioxide concentrations on soil carbon by excavating soil from large pits that were nearly three feet deep.

Researchers saw an increase in soil carbon storage under elevated carbon dioxide concentrations, a finding that was different from the other FACE experiments in forests.

Researchers found the increase in carbon storage even in deeper soil.

"Under elevated carbon dioxide, the trees were making more, deeper roots, which contributed to the accumulation of soil carbon," Iversen said.

Iversen pointed out that processes such as microbial decomposition and root dynamics change with soil depth, and information on processes occurring in deeper soil will help to inform large-scale models that are projecting future climatic conditions."

End excerpt.

Soooo,

Another negative feedback is discovered. Increase atmospheric CO2 and you get plants dumping more carbon into the ground.